Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2018	Nov. 30, 2017
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 49,224	$ 95,463	$ 118,988	$ 211,879
Less: Allocation of earnings and dividends to participating securities		(460)	(1,313)	(936)	(2,828)
Net income available to common shareholders - basic		48,764	94,150	118,052	209,051
Add: Undistributed earnings reallocated to unvested shareholders			3		7
Add: Allocation of earnings and dividends to participating securities				936
Add: Income effect of contingently issuable shares			1,379		2,756
Net income available to common shareholders - diluted		$ 48,764	$ 95,532	$ 118,988	$ 211,814
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		131,058	131,163	131,467	131,204
Average diluted options and awards		609	514	1,811	544
Additional shares issuable assuming conversion of convertible securities	[1]		3,915		3,915
Total shares for diluted earnings per share	[2]	131,667	135,592	133,278	135,663
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 0.37	$ 0.72	$ 0.90	$ 1.59
Diluted Earnings Per Share of Common Stock		$ 0.37	$ 0.70	$ 0.89	$ 1.56

[1] Represents the number of shares that would be issued if our contingently convertible notes were converted. We include these shares in the calculation of diluted EPS as the conversion of the notes may be settled, at our election, in cash, shares of our common stock, or a combination of cash and shares of our common stock. On November 27, 2018, we redeemed all of our 2.25% convertible senior notes due 2020

[2] There were no shares of restricted stock identified as being anti-dilutive for the three or six months ended November 30, 2018. Restricted shares totaling 123,262 and 99,612 for the three and six months ended November 30, 2017, respectively, were excluded from the calculation of diluted earnings per share because the grant price of the restricted shares exceeded the average market price of the shares during the period and their effect, accordingly, would have been anti-dilutive. In addition, stock appreciation rights (SARs) totaling 480,000 and 890,000 for the three and six months ended November 30, 2018 and 600,000 for the three and six months ended November 30, 2017, were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive.